The present disclosure relates in general to the field of methods of operating magnetic tapes and tape drive systems. In particular, it is directed to systems and methods relying on a gas flow (e.g., air) that impinges on the tape to locally urge it against a tape head transducer area. Related tape drives are also disclosed.
Various data storage media or recording media such as magnetic tape, magnetic disks, optical tape, optical disks, holographic disks or cards are known, which allow for storage and retrieval of data. In magnetic media, data are typically stored as magnetic transitions, i.e., they are magnetically recorded in the magnetic layer of the media. The data stored is usually arranged in data tracks. A typical magnetic storage medium, such as a magnetic tape, usually includes several data tracks. Data tracks may be written and read individually, or sets of data tracks may be written and read in parallel. Transducer (read/write) heads are positioned relative to the data tracks to read/write data along the tracks, at the level of or under the tape-bearing surface of the tape head, in which are embedded magnetic read and write transducers.
To write and read at high areal densities as used by modern tape systems, the magnetic tape has to come in close proximity to the read/write elements on the tape head. To sustain areal density improvement, modern tape systems feature ever decreasing spacing between the head and the magnetic layer-coated side of the tape as the tape is streamed by the head. Research efforts are accordingly spent to achieve viable solutions to reduce the distance between the tape and the head, as reducing this gap is what allows for increasing the areal density. The current technology typically requires a tape-head spacing of several tens of nanometers.
Historically, tapes used to be simply run wrapped over a curved-surface head, causing a layer of stable, compressed air to appear between the two surfaces when streaming the tape, and giving rise to moderate Couette flow shear stress (friction). The thickness of this air bearing is however relatively large, limiting system performance (the air bearing prevents the tape to come in close contact with the head), and is strongly dependent on the tape velocity.
To decrease the spacing and make it less dependent on velocity, various techniques have been developed, which typically rely on engineering the tape head to modify the air flow and local pressure field in the vicinity of the tape-head interface. Such techniques result in an underpressure occurring in the space between the tape and the head relative to the ambient, resulting in a pressure exercised on the section of tape overlapping the head, which pushes this section towards the head surface.
According to the main method in use today, this underpressure is obtained thanks to tape heads with skiving (i.e., sharp) edges, to scrape (or skive) off the air. That is, the underpressure is obtained by skiving the air boundary layer off the tape, which is run at a positive wrap angle over a sharp leading edge of the head, as illustrated in FIG. 1. This results in a low-pressure region directly after the skiving edge, such that the tape is pushed into intimate contact with the tape head, due to the higher air pressure on the opposite side of the tape. An advantage of this solution is that the tape-head spacing is relatively small and stable over a wide range of tape speeds. A disadvantage is the friction (which limits performance) and wear (which limits the operable lifetime of both tape and head) that arise due to the direct contact and the high pressure with which the tape is pushed into contact with the head. Furthermore, the tape is in contact over the whole width (as measure along axis z in FIG. 1) of the head, again causing undesirable friction. In extreme cases, friction can even cause the tape drive motors to stall and tape breakage.
To prevent excessive friction, the tape can be intentionally made rough, i.e. with sporadic bumps on the tape surface so that only a fraction of the tape surface is in actual contact with the tape bearing surface of the head. Effectively, these bumps increase the tape-head spacing. To increase the linear density, one may seek to reduce the tape-head spacing by using a smoother tape. However, using smoother media again results in an increased friction that can degrade the recording and read back performance of the tape drive.